Industrial process and apparatus



May 21, 1968 GABRIEL ET AL. 3,384,035

INDUSTRIAL PROCESS AND APPARATUS Filed June 2, 1965 INVENTORS. HARRYGABRIEL JOHN M. ALEXANDER,JR.

B M AM H. AMILTON a! II M ATTORNEY United States Patent 3,384,035INDUSTRIAL PROCESS AND APPARATUS Harry Gabriel, Churchville, and John M.Alexander, Jr.,

and William H. Hamilton, Philadelphia, Pa., assignors to PennsaltChemicals Corporation, Philadelphia, Pa.,

a corporation of Pennsylvania Filed June 2, 1965, Ser. No. 460,779Claims. (Cl. 107-17) ABSTRACT OF THE DISCLOSURE In a rotary tablettingmachine the means for adjusting the vertical position of the pull-downcam while the machine is in operation correspondingly adjusts the levelof the lower tablet punch in its lowermost position during thedie-filling operation.

This invention relates to means for moving the punches of rotarytabletting machines. More specifically the invention relates to meansfor controlling the lowering of the lower punches of such machinesduring the die-filling operation.

In the rotary tabletting machines of the prior art a rotary table haspresented dies spaced uniformly about it and has carried over the diesand under the dies a series of aligned cooperating verticallyreciprocable punches. Material has been deposited onto the table, thelower punches have been lowered successively to a lower extreme orinitial fill position and material has been scraped into the associateddies. The lower punches have been then raised to adjust accurately thevolume and hence weight of the material in each die, and overfillmaterial has been scraped off the top of the die. The upper and lowerpunches have been brought together into the die under great pressure byappropriate cams or rolls. Subsequently the lower punch has been raisedto eject the finished tablet out of-the die and the finished tablet hasbeen moved off the table.

The drawing of the lower punch down to a low initial fill positionbefore raising it to the weight adjusting level has assured that the dieis totally filled when the lower punch is raised to the weight adjusterposition.

In prior art machines the weight adjuster cam has been movable up ordown while the machine is running to adjust the weight of material inthe tablet products, If, for instance, the bulk density of one batch ofmaterial to be tabletted is relatively low, the cam may be set lower toaccept more volume of material than in a second batch which is of higherbulk density. In this fashion the weight of the tablets in the twobatches will be uniform.

The adjustment of the weight adjuster cam to a high level has broughtthe problem, especially in large diameter tablets, of flooding thetabletting machine with an excess of overfill scrapings. This rejectedmaterial has accumulated in excess on the die table and has spilt overthe feed frame back into the die cavities causing varying tablet weight.Excess material has also worked out into the dies causing varying tabletweights and has been thrown off of the table altogether to result insloppy operation and much wastage. Free loose powder has in this mannerworked its way into the finished tablet receptacle. A separate problemhas arisen in instances in which the overfill has been high: thescrape-off operation has sometimes left a concavity in the top of thefill in the die causing an underweight tablet.

To avoid the wide difference between the extreme low point or initialfill position and the high settings of the weight adjuster cam and itsconsequent problems, filler plates and lesser drop pull down cams havebeen selectively installed in the machine to raise the low point. Theselective replacement of these cams and filler plates, however, has beenunsatisfactory since it has required a stoppage of the machine and apartial disassembly. It has also required the expense and storage ofmultiple extra sets of filler plates and cams.

In accordance with the present invention there is provided means toadjust the position of the pull-down cam while the tabletting machine isin operation. The distance between the initial fill position and theweight adjuster cam can thus be kept constant as the position of theweight adjusting cam is changed.

A feature of the invention involves means to assure that as thepull-down cam is lowered its inclined portion remains in constantrelative position with respect to the horizontal. This results in evenand uniform contact of the cam and the punches and avoids binding andexcessive wear of the punches against the cam.

Other features of the invention will be apparent from the followingspecification including the drawings wherem:

FIGURE 1 represents a fragmentary top view of an apparatus embodying theinvention and taken above the pull-down cam;

FIGURE 2 is a fragmentary sectional view on line 22 of FIGURE 1 showingthe pull-down cam and the weight adjuster cam with the upper punchesshown in phantom; and

FIGURE 3 is an enlarged sectional view taken on line 3-3 of FIGURE 2.

Briefly, in a rotary tabletting machine, the invention comprises meansfor adjusting the vertical position of the pull-down cam while themachine is in operation to correspondingly affect the level of thelowermost position of the lower tablet punch during the die-fillingoperation.

Referring more specifically to the drawings, an apparatus embodying theinvention is shown in FIGURE 2. It comprises a rotary table 12 whichmounts a plurality of dies 14. Lower punches 16 are mounted in the tablein openings under the dies 14 while upper punches 18 (shown in phantom)are mounted in another portion of the rotary table (not shown) and areadapted to cooperate with the lower punches 16 to compress tabletmaterial in the dies 14. Each of the punches is formed with a head 16aby which the vertical movement of the punch is adapted to berestrictively controlled.

Mounted on frameztl under the table 12 is a stationary pull-downcarnsection 22. This section comprises a pair of inwardly directedspaced tracks 24 which engage successively the top bevel portions of theheads 16a of the lower punches. As shown in FIGURE 1 the stationarysection of the pull-down cam is formed with a longitudinal recess 26.

Positioned above the frame 20 adjacent the cam section 22 is movablepull-down cam section 28. This section is provided with a floor 30 and,like the section 22,

is provided with inwardly directed spaced tracks 32 to engage each punchhead 16a. The movable section 2.8 of the cam is provided with a tongueelement 34 which extends into the recess 26 to make a continuous limitfor the lowermost position of the head 16a, should the punch fall undergravity.

To the left of the movable section 34 of the pull-down cam as shown inFIGURE 2 is the weight adjuster cam 36. As shown in FIGURE 1 the weightadjuster cam 36 is adapted to engage the head 16a as the punch moves inthe rotation of the table 12.

It will be understood that as the table 12 rotates in the direction ofthe arrow (FIG. 2) the lower punches first engage the pull-down cam 22,28 and are drawn down to an extreme low point. They subsequently areengaged by the 3 weight adjuster cam 36 and are raised to the accurateweight fill level as indicated by the punch 16'. Overfill materialrejected above the die 14 is leveled off by a fixed scraper or doctor(not shown). The lower punch then may fall to the dwell cam 37 beforethe pressure means brings the punches together in the die.

The weight adjuster cam 36 is supported on a shaft 38. The lower end ofthe shaft is reduced and threaded at 40 and receives a bevel gear 42,the central opening of which is correspondingly threaded. The shaft 38is vertically movable, but is held against rotation by being secured tothe cam 36 which itself is confined by set screws 39 in the cam 37.Journaled \in the gear box frame 44 is a crank shaft 46 which fixedlymounts a second bevel gear 48. With this arrangement the turning of thecrank 50 will adjust the vertical position of the weight adjuster cam36.

The movable section 28 of the pull-down cam is supported on 'a pair ofstuds 52 and 54 which extend through openings in the frame 20. Mountedon the underside of the frame is the drive sleeve housing 56 which isformed with openings to receive respectively the internally threadedsleeves 58 and 60'. The sleeves carry outward flanges about their upperends which are supportingly engaged by the housing 56. The sleeves arefree to rotate in the housing.

The sleeves 58 and 60 extend downward and terminate in reduced shafts 62and 64 respectively. These shafts are appropriately journaled inbushings in the pull-down cam gear box 66 and are coupled for rotationby sprockets 68 and 70 over which is trained a chain 72. By this meanssleeves 58 and 56 are made to rotate in unison and since the threads inthe sleeves are matching, the studs 52 and 54 rise and fall in unisonassuring that the movable section 28 of the pull-down cam remains inconstant position with respect to the horizontal.

To drive the shafts 62 and 64 a bevel gear is fixedly mounted on theshaft 62. Engaging this bevel gear 74 is a second bevel gear 76 which ismounted on a drive shaft 78 journaled in the gear box frame 66.Rotatably linking the crank shaft 46 and drive shaft 78 are a pair ofsprockets 80 and 82 over which is trained the chain 84.

By means of the arrangement shown when the crank 50 is turned, theweight adjuster cam and the movable section 28 is raised or lowered. Thethreads on the stud shafts, the ratios of the sets of bevel gears, andthe relative sizes of the chain sprockets are such that the movement ofthe weight adjuster cam will be met by a similar movement of the movablesection 28.

For independent movement of the weight adjuster cam withoutcorresponding movement of the movable section 28 as is desired insetting the overfill distance, sprocket 82 may be disengaged from theshaft 78 and the shaft turned. When the section 28 has reached thedesired relationship to cam 36, sprocket 82 is -re-engaged. A variationof the structure involves two separate hand cranks, one for shaft 46 andone for shaft 78, eliminating the sprockets 80 and 82 and the chain 84and providing totally independent control for the two cams. Since formost operations the overfill may remain constant, independent control isusually neither desirable or necessary.

As shown in FIGURE 2 a fixed section 22 of the pulldown cam willassuredly lower the lower punch 16 so that the head 16a is at a leveljust below the point A. The movable section 28 of the pull-down cam willassure that the head 16a is further lowered to a point at which the head16a is immediately below the movable point B. Point B can be raised orlowered. The floor of the movable section 28 limits downward movement ofthe head 16a should the punch fall down and not need to be drawn down bythe tracks 32. While there is considerable distance between the tracks32 and the floor 30 adjacent the stationary section 22 of the pull-downcam, at the point B the distance closes down so that control over theposition of the head 16a is exact to afford precise posi- .4 tion'ing ofthe punch at its lowermost point whether the punch 16 falls or is pulleddownwardly.

As a result of the structure disclosed and other embodiments of theinvention, it is possible to control accurately and adjust the lowermostposition of the lower punch prior to the weight adjuster station. Thisaffords means for controlling the amount of material loose on the dietable with consequent indicated advantages. A special advantage of theembodiment shown is the constant angle maintained by the cam incline asthe section 28 is raised or lowered. This avoids excessive wear andbinding of the punches and cam.

The invention may be practiced with any kind of means including a camfor limiting the downward travel of the lower punches, whether they arethe so-called pull-down cams or those wherein cams function merely tolimit the downward travel of the lower punches which normally oroccasionally fall under gravity.

The present invention may be embodied in other specific forms withoutdeparting from the spirit or central attributes thereof and,accordingly, reference should be made to the appended claims rather thanthe foregoing specification as indicating the scope of the invention.

We claim:

1. A tabletting machine comprising a stationary frame, arotary tablesupported on the frame, dies and cooperating upper and lower punchesmounted on the table, means including a first cam for limiting thedownward travel of the lower punches and a weight adjuster second camdisposed under the table and adapted respectively to engage the lowerpunches successively to lower them to a low initial fill position andthen raise them to a position for accurate weighted fill, and means onthe frame adjustably supporting the two cams whereby the cams may beadjusted in vertical disposition either independently or in unison whilethe table is rotating for controlling the extent of overfill during theinitial filling of the dies as well as for accurately controlling theweight of the fill.

2. A tabletting machine as described in claim 1 wherein the means foradjustably supporting the first cam comprises a pair of spaced supportsand means adapted to move the supports in unison to maintain the firstcam in constant relation to the horizontal.

3. A tabletting machine as described in claim 2 wherein the means tomove the supports in unison comprise rotatable threaded elementsrotatably linked together.

4. A tabletting machine as described in claim 1 wherein the first camhas inwardly directed tracks and the lower end of the lower punches haveenlarged heads and are adapted to be engaged on the heads by the saidtracks.

5. A tabletting machine as described in claim 4 wherein the first cam isformed with a floor spaced below and intermediate the tracks, said floorbeing adapted to engage the lower surface of the punch, and the verticaldistance between the tracks and the floor decreases as the weightadjuster cam is approached.

6. In a tabletting machine comprising a frame, a horizontally disposedrotary table mounted on the frame and carrying a plurality of dies, aplurality of upper and lower punches mounted in the table above andbelow the dies respectively for movement toward and away from the dies,means including a first cam for limiting the downward travel of thelower punches being disposed below the table and adapted to engage alower portion of the lower punches successively as the table rotates tolower the punches to a low initial fill position, and a weight adjustersecond cam adjustably mounted on the frame adjacent the first cam tosubsequently raise the lower punches to a desired fill position, theimprovement wherein at least a portion of the first cam proximate theweight adjuster second cam is supported on the frame by adjustablesupport means, said cams being also capable of relative adjustment.

7. A tablet-ting machine as described in claim 6 wherein the means foradjustably supporting the first cam portion 5 comprises a pair of spacedsupports and means adapted to move the supports in unison to maintainthe first cam portion in constant relation to the horizontal.

8. A tabletting machine as described in claim 7 wherein the means tomove the supports in unison comprise rotatable threaded elementsrotatably linked together.

9. A tabletting machine as described in claim 6 wherein a second portionof the first cam is disposed on the opposite side of the first portionfrom the weight adjuster cam, and the second portion is formed with alongitudinal recess and the first portion is formed with a tongueextending into the recess to provide a continuous lower limit for thelower punches.

10. A tabletting machine as described in claim 6 including means tooperate the first cam portion and the weight adjuster cam in unison.

References Cited UNITED STATES PATENTS 2,043,085 6/1936 Westin et a1107-17 2,218,913 10/ 1940 Hughes et al. 15-77 2,321,179 6/1943 Boyer15-77 2,997,741 8/ 1961 Crossley 10717 X 3,029,752 4/1962 Frank 107-17WALTER A. SCHEEL, Primary Examiner.

A. O. HENDERSON, Assistant Examiner.

